1. Field of the Invention
This invention is in the field of Otto cycle internal combustion engines and in particular relates to apparatus for conditioning a premixed homogenous charge supplied to such engines.
2. Description of the Prior Art
Otto cycle internal compustion engines using normally liquid hydrocarbon fuels require that the fuel be vaporized in the intake airstream before reaching the combustion chambers of the engines. While complete vaporization of the fuel is necessary for enabling the engine to operate at maximum efficiency, in actual practice it has been observed that after the fuel has been added to the intake airstream, it may condense out on the walls of the intake manifold of the engine or may otherwise condense into droplets before reaching the combustion chambers. While the fuel/air charge is generally considered as being a homogenous mixture of the reactants, in actuality they can be considered more precisely as being constituted of air, fuel vapor, suspended minute fuel particles (droplets) and a liquid film of unvaporized or condensed fuel. Due to the different physical properties of these charge constituents, the rate of flow from the charge forming device, e.g., a carburetor, to each working chamber of the engine is varied, and results in different fuel/air proportions in different working chambers. This, as is generally recognized, produces less than desirable engine performance, including rough idling, misfire, poor economy and related problems that prevent the engine from achieving theoretical expectations for the fuel supplied in the charge.
To counteract these problems, various means are utilized in conventional internal combustion engines to provide heat to the intake manifold and still other refinements have been proposed by way of fuel charge preheaters that elevate the temperature of the charge before it reaches the combustion chambers of the engine. However, prior art heaters usually constitute heat exchangers and do not involve the admixture of another heated gaseous component into the charge stream to add heat to the charge to vaporize fuel.
It is also conventional to introduce exhaust gases into the charge intake stream of an internal combustion engine for the purpose of slightly diluting the charge to thereby reduce the temperature of the combustion zone in the working chambers of the engine during high load operation to reduce the generation of oxides of nitrogen (NO.sub.x) which are an undesirable pollutant contained in engine exhaust gases. However, the maximum quantity of exhaust gases in such systems is comparatively small and the heat content thereof is insufficient to heat the intake charge to an adequate extent to thoroughly vaporize and condition the fuel, so that the basic problems associated with the supply of premixed, homogenous charges still remain even with such recirculating systems installed.